Apparatus and method for sampling downhole fluids

ABSTRACT

Tools and methods for downhole sample analysis are provided. An apparatus for sampling a downhole fluid includes a tool having at least one surface element wetted by a downhole fluid such as drilling fluid, return fluid or production fluids such as asphaltenic hydrocarbons. At least one surface element disposed on the tool can include a fluid-repellent material disposed on a substrate for repelling at least a portion of the downhole fluid wetting the surface element.

BACKGROUND TECHNICAL FIELD

The present disclosure generally relates to downhole tools and inparticular to systems and methods for downhole fluid sampling.

BACKGROUND INFORMATION

Oil and gas wells have been drilled at depths ranging from a fewthousand feet to as deep as five miles. A large portion of the currentdrilling activity involves directional drilling that includes drillingboreholes deviated from vertical by a few degrees to horizontalboreholes to increase the hydrocarbon production from earth formations.

Information about the subterranean formations traversed by the boreholemay be obtained by any number of techniques. Techniques used to obtainformation information include obtaining one or more core samples of thesubterranean formations and obtaining fluid samples produced from thesubterranean formations these samplings are collectively referred toherein as formation sampling. Modern fluid sampling includes variousdownhole tests and sometimes fluid samples are retrieved for surfacelaboratory testing.

Typical downhole fluids can include drilling fluids, return fluids, andproduction fluids containing one or more hydrocarbons. Downhole fluids,depending on composition, temperature, and pressure, can be viscousand/or adhesive in nature. For example, production hydrocarbons caninclude one or more viscous and/or adhesive asphaltenic compounds, eachhaving twenty or more carbon atoms. Surface-based fluid analyses anddownhole fluid analysis are often affected due to the inability toproperly purge downhole fluid samples from test cells and frominstrument sensors. Fluid buildup on downhole instrument sensors canundesirably increase response time and may cause an unwanted offset insignal response.

SUMMARY

The following presents a general summary of several aspects of thedisclosure in order to provide a basic understanding of at least someaspects of the disclosure. This summary is not an extensive overview ofthe disclosure. It is not intended to identify key or critical elementsof the disclosure or to delineate the scope of the claims. The followingsummary merely presents some concepts of the disclosure in a generalform as a prelude to the more detailed description that follows.

Disclosed is an apparatus for sampling a downhole fluid. The apparatuscan include a tool having at least one surface element wetted by adownhole fluid, and the at least one surface element may include afluid-repellant material disposed on a substrate for repelling some orall of the downhole fluid wetting the at least one surface element.

An exemplary method for sampling a downhole fluid includes wetting atleast one surface element of a tool with a downhole fluid the at leastone surface element comprising a fluid-repellant material disposed on asubstrate. The method may further include repelling some or all of thedownhole fluid from the at least one surface element.

An exemplary method for manufacturing an apparatus for sampling adownhole fluid includes disposing a fluid-repellant material on asubstrate to form a surface element. The manufacturing method furtherincludes forming at least a portion of a downhole fluid sampling toolusing the surface element, the surface element being wettable by adownhole fluid during operation of the downhole fluid sampling tool.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed understanding of the present disclosure, reference shouldbe made to the following detailed description of the severalnon-limiting embodiments, taken in conjunction with the accompanyingdrawings, in which like elements have been given like numerals andwherein:

FIG. 1 schematically represents a non-limiting example of anillustrative tool for conducting a downhole operation according to oneor more embodiments of the disclosure;

FIG. 2 shows a cross-sectional view of an exemplary surface elementaccording to one or more embodiments of the disclosure;

FIG. 3 depicts a non-limiting example of an illustrative device crosssection showing a surface element having a coated substrate according toone or more embodiments of the disclosure;

FIG. 4 is a non-limiting elevation view of an exemplary well loggingapparatus according to several embodiments of the disclosure; and

FIG. 5 is a non-limiting elevation view of an exemplary simultaneousdrilling and logging system that incorporates several aspects of thedisclosure.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 schematically represents a non-limiting example of anillustrative tool 100 for conducting a fluid sampling operationaccording to one or more embodiments of the disclosure. The tool 100 maybe disposed within or about a carrier 134. The carrier 134 may be asurface-located carrier or may be used for transporting the tool 100into a well borehole. The tool 100 may include any number of devices forconducting downhole operations. The tool devices shown in the example ofFIG. 1 include a spectrometer 104, and a sensor test section includingsensors 118, 120, 122, 124, and a sensor interface 138 and one or moresample chambers 116. A downhole computing device 128 having a processor130 and a data storage unit 132 is shown coupled to the spectrometer 104and to the sensor section via a communications bus 136. Informationprocessed in the computing device 128 may be transmitted via the bus 136to other devices including, but not limited to, controllers, loggers,transmitters, or any combination thereof. The communication bus 136 caninclude one or more optical and/or one or more electrical cables asdesired for a particular tool configuration. These and similar devicesmay be used for sampling and testing downhole fluids sampled by the tool100.

In the non-limiting example of FIG. 1, a pump 142 is in fluidcommunication with fluid conduits 112 and one or more ports 102 forpermitting downhole fluids to flow into the tool 100 and through, into,and/or around the one or more devices disposed within the carrier 134.Sampled downhole fluids may be expelled from the tool 100 via one ormore outlet ports 114 positioned as desired on the carrier 134 and influid communication with the fluid conduits 112. The downhole fluids mayinclude, but are not limited to, polar and non-polar drilling fluids,return fluids, and/or formation fluids. The downhole fluids may includeone or more hydrocarbon species containing twenty or more carbon atoms,for example asphaltenes having one or more viscous, high molecularweight hydrocarbons. These highly viscous, and often adhesive, downholefluids may tend to buildup on wetted surface elements 200 of downholeand/or uphole devices and on the surface elements 300 of other devicesthat contact the downhole fluids during sampling or testing. Severalexemplary downhole devices such as the spectrometer 104, sensors 118,120, 122, 124 and/or fluid sample chambers 136 include respectivesurface elements 200, 300 that will contact downhole fluid as depictedin the exemplary embodiment of FIG. 1.

Still referring to FIG. 1, the downhole fluid may flow through fluidconduits 112, to the spectrometer 104. An exemplary spectrometer 104 mayinclude a light source 106, a sample region 108, and one or moredetectors 110, 111 for measuring the optical properties of downholefluid within a fluid sample region 108. The fluid sample region 108includes a surface element 200 in contact with fluid in the fluid sampleregion 108. The downhole fluid may be conveyed via the fluid conduits112 to a valve 144 that may be actuated to convey the downhole fluid toa test section where a sensor interface 106 may be coupled to sensors,such as the sensors 118, 120, 122, and 124 mentioned above that haverespective surface elements 300 contacting the downhole fluid flowing inthe test section. The sensors 118, 120, 122, 124 may include any numberof sensor types. For example, sensors in the test section may include atemperature sensor 118, a pressure sensor 120, a stress sensor 122, adistance sensor 124 as shown or any other sensor type that may be usefulin estimating downhole fluid properties. The exemplary temperaturesensor 118 can include at least one temperature sensitive device, forexample a thermocouple, thermistor, resistance temperature detectors(RTD), or any combination of one or more devices, suitable forconverting the temperature of the fluid flowing past the sensor into oneor more signals. The pressure sensor 120 can include at least onepressure sensitive device, for example a mechanical deflection sensor,strain gauge, piezoresistive semiconductor sensor,micro-electromechanical system (MEMS) sensor, vibrating element sensor,variable capacitance sensor, or any combination thereof. The one or morestress sensors 122 can include one or more acceleration and/or vibrationsensors. Downhole fluid may be expelled before or after entering thetest section or may be retained for later testing.

In some embodiments, the valve 144 may be actuated to expel the downholefluid from the tool via an outlet port 114 positioned upstream of thetest section. The downhole fluid may be further conveyed via the fluidconduits 112 to an outlet port 114 downstream of the test section or maybe directed via a valve 146 to the sampling chamber 116. In someembodiments, the sampling chamber may be flushed using another valve 148and outlet port positioned downstream of the sampling chamber 116. Thesampling chamber 116 may include a surface element 200 that is incontact with fluid in the sampling chamber 116. The several surfaceelements 200, 300 are further described below with reference to FIGS. 2and 3.

FIG. 2 shows a cross-sectional view of an exemplary surface element 200according to one or more embodiments of the disclosure. A surfaceelement 200 according to several exemplary embodiments includes asubstrate 210 with a surface portion 205 comprising a fluid-repellentmaterial 220. The surface portion 205 may be chemically and/ormechanically bonded to the substrate 210. The fluid-repellent material220 may be selected to prevent the buildup and/or adhesion of thedownhole fluid 215 to the surface portion 205, thereby improving theflow of the downhole fluid 215 past or along the coated substrate 210.The fluid-repellent material 220 can include, but is not limited to,polytetrafluoroethylene (PTFE) compounds, fluorocarbon resins,fluoropolymers, silicone polymers, mixtures thereof and/or combinationsthereof. The fluid-repellent material 220 can be applied to thesubstrate during or after fabrication of the wetted surfaces in both thetool 100 and the carrier 134 thereby providing a fluid-repellent surfaceportion 205 on the wetted surfaces. The fluid-repellent material 220 canbe applied as a liquid, solid, or gas through any deposition processamenable to providing a continuous, non-porous coating on the selectedwetted surfaces within the carrier 134. For example, the fluid-repellentmaterial 220 can be applied to the substrate 210 using applicationtechniques including, but not limited to, powder coating, spraying,immersion, electrostatic precipitation or deposition, gas phasecondensation, or any combination thereof. The surface element 200 may beincorporated as a portion of any number of the fluid-contacting surfacesdescribed above and shown in FIG. 1. In some examples, the surfaceelement 200 may form a portion of a sensor that contacts downhole fluidsas described below with reference to FIG. 3.

FIG. 3 depicts a non-limiting example of an illustrative device crosssection 300 showing a surface element 200 having a coated substrate 210according to one or more embodiments of the disclosure. The substrate210 can include any wetted internal or external surface disposed in, on,or about the tool 100 and/or carrier 134. The exemplary view of FIG. 3shows one or more sensors 305 disposed on the substrate 210. The sensors305 can be in fluid and/or electrical communication with other elements,components and/or devices within the carrier 134 via one or moreelectrical conductors and/or fluid conduits shown schematically at 310.The sensors 305 may include, but are not limited to, one or morepressure sensors, temperature sensors, optical sensors, fluorescencesensors, flow rate sensors, viscosity sensors, or any combinationthereof. The sensors 305 can include one or more wavelength specificlight generators and/or receivers. Where the one or more sensors 305include optical devices such as optical sensors, wavelength specificlight generators and/or receivers, the fluid-repellent material 205disposed on or about the sensor 305 can be translucent and/ortransparent to one or more selected light frequencies generated and/orreceived by the one or more sensors 305. The several sensor embodimentsmay be incorporated into a tool 100 for sampling downhole fluids asdescribed above and shown in FIG. 1, and as mentioned, the tool may 100a surface tool or a downhole tool. Downhole tools may be conveyed viawireline or drill string as described below.

FIG. 4 shows a non-limiting example of a well logging apparatus 400according to several embodiments of the disclosure. The well loggingapparatus 400 is shown disposed in a well borehole 402 penetrating oneor more formations 404 for making measurements of properties of theformations 404. The borehole 402 is typically filled and/or pressurizedwith drilling fluid to prevent formation fluid influx.

A tool string 406 can be lowered into the well borehole 402 using one ormore cables 408 that can be spooled and unspooled using a winch or drum410. At least one of the cables 408 can be an armored communicationscable containing one or more communications buses 136. The tool string406 can be in two-way communication with surface equipment 412 using thecommunications cable 136, containing one or more optical fibers and/orelectrical conductors, within the armored communications cable 408. Asdepicted in FIG. 4, the tool string 406 can include one or more tools100 as described in detail with respect to FIG. 1 above. The tool string406 can preferably be centered within the well borehole 402 using one ormore centralizers 422 a, 422 b attached to the tool string 406 ataxially distant locations. The centralizers 422 a, 422 b can be of typeswell known in the art, such as bowsprings.

The surface equipment 412 can include one or more telemetry systems 414for communicating control signals and data to the tool string 406 andone or more computers 416. The computer 416 can include one or morerecorders 418 for storing, plotting, and/or recording data acquiredusing the one or more downhole tools 100 and transmitted via thecommunications bus 136 to the surface equipment 412. Circuitry forcontrolling and operating the one or more tools 100 can be locatedwithin the tool string 406, for example within one or more electronicscartridges 424. The circuitry can be connected to the one or more tools100 using one or more connectors 426. In several embodiments, the tool100 can incorporate one or more high-gain semiconductor devices such asone or more of the devices described herein with respect to FIG. 1, FIG.2, and/or FIG. 3.

FIG. 5 is an elevation view of a simultaneous drilling and loggingsystem 500 that may incorporate non-limiting embodiments of thedisclosure. A well borehole 502 can be drilled into the earth undercontrol of surface equipment including a drilling rig 506. In accordancewith a conventional arrangement, rig 506 includes a drill string 514.The drill string 514 can be a coiled tube, jointed pipes or wired pipesas well known by those skilled in the art. In one example, a bottom holeassembly (“BHA”) 550 may include one or more tools 100 such as one ormore of the devices described herein with respect to FIG. 1, FIG. 2,and/or FIG. 3.

While-drilling tools will typically include a drilling fluid 526circulated from a mud pit 528 through one or more mud pumps 530, pastone or more desurgers 532, and through one or more mud supply lines 534.The drilling fluid 526 can flow through a longitudinal central bore inthe drill string 514 exiting through one or more jets (not shown)disposed about the lower face of a drill bit 524. Return fluidcontaining drilling mud, cuttings and formation fluid can be returned tothe surface via the annular region 538 that exists between the outersurface of the drill string 514 and the inner surface of the borehole502. Return fluid exiting the annular region 538 can be directed vialine 542 to the mud pit 528 for analysis, recovery, recycle and/ordisposal.

The system as depicted in FIG. 5 can use any conventional telemetrymethods and devices for communication between the surface and one ormore downhole components and/or tools 100. In the embodiment shown mudpulse telemetry techniques can be used to communicate data from downholeto the surface during drilling operations. A surface controller 548 canbe used for processing commands and other information used in thedrilling operations.

In one or more embodiments, a downhole drill motor 536 can be includedin the drill string 514 for rotating the drill bit 524. In severalembodiments, the while-drilling tool 100 can incorporate one or morehigh-gain semiconductor devices such as any of the devices describedherein and shown in FIGS. 1 through 3.

A telemetry system 552 may be located in a suitable location on thedrill string 514 such as above the tool 100. The telemetry system 552may be used to transmit and/or receive commands and/or data to thesurface controller 548 using mud pulse telemetry or by othercommunication techniques known in the art. For example, acoustic pipetelemetry and/or wired pipe telemetry may be used.

The surface controller 548 can include one or more data processingsystems, one or more data storage systems, one or more data recordingsystems, one or more data handling peripherals, or any combinationthereof. The surface controller 548 can also respond to user commandsentered through a suitable man-machine interface, such as a keyboard. Inone non-limiting embodiment, the BHA 550 can incorporate various aspectsof the disclosure, including, but not limited to, sensors andlogging-while-drilling (LWD) devices to provide information about theformation, downhole drilling parameters and the mud motor.

Several operational examples will now be described with reference to theseveral exemplary embodiments described above and shown in FIGS. 1-5. Inone or more exemplary embodiments, the illustrative tool 100 as depictedin FIG. 1 can be deployed downhole via wireline or while drilling, asdescribed above and shown in FIG. 4 and FIG. 5. A downhole fluid can besampled by introducing a portion of the downhole fluid into the tool 100via the inlet port 102 disposed about the carrier 134. Within the tool100, the downhole fluid can be pumped using the pump 142 to convey thedownhole fluid through one or more fluid conduits 112, to other devicesin the tool 100.

In this operational example, the fluid is conveyed to the spectrometer104 where properties of the fluid within the sample region 108 areestimated based upon the transmissive, refractive and/or reflectiveproperties of the fluid within the sample region 108. Fluid leaving thesample region 108 may be directed to an outlet port or to a fluid testsection using the valve 144 installed at the discharge of the sampleregion 108 in the spectrometer 104. The fluid contacting the surfaceelement 200 of the sample chamber 108 is repelled from the surfaceelement by the fluid repellent material 220 forming a portion or thesurface element 200. Fluid may be discharged from the tool for anynumber of reasons. Sometimes the fluid is discharged until the fluidcontent is substantially free of wellbore fluids so that fluid enteringthe test section is substantially pristine formation fluid. Having afluid repellent material as a portion of the surface element helps toprovide self cleaning for the sample region 108. When further testing isdesired, then the fluid is directed to the test section via the valve144, to the several sensors 118, 120, 122, and/or 124 in the testsection.

The physical properties of the fluid in the test section, such asdensity, and downhole conditions such as temperature and pressure, areestimated using the sensors 118, 120, 122, 124. The fluid repellentmaterial 220 forming a portion of the surface element 300 of the severalsensors helps repel fluid from the sensor surfaces contacting the fluid.In this manner, the sensor sensitivity may be better maintained due inpart to keeping the sensing surface clean of fluid residue. Fluidpassing through the test section may be directed to the outlet port 114downstream of the test section or to the fluid sample chamber 116 viathe fluid conduits 112.

The fluid contained within the sample chamber 116 may be retained forlater analysis by closing the two-way valve 148 located on the dischargeof the sample chamber 116. Alternatively, the fluid within the samplechamber 116 can be rejected from the tool 100 by opening the two-wayvalve 148, permitting the fluid within the sample chamber 116 to flowthrough the fluid conduit 112 to the discharge port 114. The fluidrepellent material 220 used as a portion of the sample chamber surfaceelement helps when flushing fluid samples from the sample chamber.

The present disclosure is to be taken as illustrative rather than aslimiting the scope or nature of the claims below. Numerous modificationsand variations will become apparent to those skilled in the art afterstudying the disclosure, including use of equivalent functional and/orstructural substitutes for elements described herein, use of equivalentfunctional couplings for couplings described herein, and/or use ofequivalent functional actions for actions described herein. Suchinsubstantial variations are to be considered within the scope of theclaims below.

1. An apparatus for sampling a downhole fluid comprising: a tool havingat least one surface element wetted by a downhole fluid, the at leastone surface element including a fluid-repellant material disposed on asubstrate for repelling some or all of the downhole fluid wetting the atleast one surface element.
 2. The apparatus of claim 1, wherein the toolis wetted by the downhole fluid while deployed downhole via wireline orwhile drilling.
 3. The apparatus of claim 1, wherein the tool is wettedby the downhole fluid while deployed in a surface location.
 4. Theapparatus of claim 1, further comprising one or more fluid testinstruments having one or more surface elements.
 5. The apparatus ofclaim 4, wherein the tool includes one or more sensors exposed to thedownhole fluid.
 6. The apparatus of claim 5, wherein the one or moresensors comprise one or more pressure sensors, temperature sensors,viscosity sensors, density sensors, optical sensors, fluorescencesensors, and flow rate sensors.
 7. The apparatus of claim 1, wherein thetool comprises a wavelength spectrum light generator and thefluid-repellant material is transparent to at least a portion of thewavelength spectrum generated by the wavelength spectrum lightgenerator.
 8. The apparatus of claim 1, wherein the downhole fluidcomprises one or more of a drilling fluid, a return fluid, and aformation fluid.
 9. The apparatus of claim 1, wherein the downhole fluidcomprises hydrocarbons having twenty or more carbon atoms per molecule.10. The apparatus of claim 1, wherein the downhole fluid comprises oneor more of a polar fluid, and non-polar fluid.
 11. The apparatus ofclaim 1, wherein the fluid-repellent material comprises one or more ofpolytetrafluoroethylene (PTFE) compounds, fluorocarbon resins,fluoropolymers, silicone polymers, and fluorocarbon polymers.
 12. Theapparatus of claim 1, wherein the fluid-repellent material comprises acoating applied to the substrate by one or more of powder coating,spraying, immersion, and electrostatic deposition.
 13. A method forsampling a downhole fluid comprising: wetting at least one surfaceelement of a tool with a downhole fluid the at least one surface elementcomprising a fluid-repellant material disposed on a substrate; andrepelling some or all of the downhole fluid from the at least onesurface element.
 14. The method of claim 13, wherein the wetting of thesurface element with the downhole fluid occurs while the tool isdeployed downhole via wireline or a drilling sub.
 15. The method ofclaim 13, wherein wetting the at least one surface element occurs whilethe tool is deployed in a surface location.
 16. The method of claim 13,wherein of a drilling fluid, a return fluid, and a formation fluid. 17.The method of claim 13, wherein wetting the at least one surface elementincludes wetting with one or more hydrocarbons having twenty or morecarbon atoms per molecule.
 18. The method of claim 13, wherein wettingthe at least one surface element includes wetting with one or more polarfluids, and one or more non-polar fluids.
 19. The method of claim 13,wherein the fluid-repellent material comprises one or more ofpolytetrafluoroethylene (PTFE) compounds, fluorocarbon resins,fluoropolymers, silicone polymers, and fluorocarbon polymers.
 20. Themethod of claim 13, wherein the fluid-repellent material comprises acoating applied to the substrate by one or more of powder coating,spraying, immersion, and electrostatic deposition.
 21. A method formanufacturing apparatus for sampling a downhole fluid comprising:disposing a fluid-repellant material on a substrate to form a surfaceelement; forming at least a portion of a downhole fluid sampling toolusing the surface element, the surface element being wettable by adownhole fluid during operation of the downhole fluid sampling tool. 22.The method of claim 21, wherein the fluid-repellent material comprisesone or more of polytetrafluoroethylene (PTFE) compounds, fluorocarbonresins, fluoropolymers, silicone polymers, and fluorocarbon polymers.23. The method of claim 21, wherein the fluid-repellent materialcomprises a coating applied to the substrate by one or more of powdercoating, spraying, immersion, and electrostatic deposition.